The engine must be completely cool when the heads are removed to prevent head warpage. If removing the left cylinder head, discharge and recover the air-conditioning refrigerant, then disconnect the cable from the negative terminal of the battery. Remove the valve cover(s), followed by the push rods and rocker arms. Next, remove the intake manifold after draining the cooling system. Take off the drive belt and drive belt tensioner, then remove the exhaust manifold(s). At the rear of the right cylinder head, remove the bolt holding the transmission dipstick tube. Loosen the cylinder head bolts in 1/4-turn increments until they can be removed by hand, working from bolt to bolt in a reverse pattern of the tightening sequence, and discard the cylinder head bolts. Lift the cylinder head(s) off the engine, using a wood block and hammer if resistance is felt, and store the heads on wood blocks to prevent damage to the gasket-sealing surfaces. Ensure the mating surfaces of the cylinder heads and engine block are perfectly clean before installation, using a gasket scraper and cleaning with lacquer thinner or acetone. Cover the lifter valley with shop rags to keep debris out, and use a vacuum cleaner to remove any debris that falls into the cylinders. Check the engine block and cylinder head mating surfaces for damage; slight damage can be removed with a file, while excessive damage may require machining. Use a tap to chase the threads in the cylinder head bolt holes and run a die down the threads of each bolt to remove corrosion. Position the new gasket(s) over the locating dowels in the engine block, ensuring correct orientation and alignment of all holes. Carefully place the cylinder head(s) on the engine block without disturbing the gasket(s). Lightly oil the threads on all new cylinder head bolts before installing them finger tight. Follow the recommended sequence to tighten the bolts in steps to the specified torque, using new cylinder head bolts. The remaining installation steps are the reverse of removal. Finally, change the engine oil and filter, then start the engine and check for oil and coolant leaks.